With an increasing demand for easier usage and better image quality, digital cameras are typically equip with automatic capture settings, particularly auto focus and auto exposure. For digital cameras based on personal electronic devices, the automatic setting is often essential.
In auto focus, many cameras, particularly the cameras attached to the personal electronic devices use a “passive autofocus”. A passive autofocus captures images at two or more candidate lens positions. The amount of blur for each image can then be determined. Conventionally, this is estimated using a contrast measure. The lens position associated with the maximum amount of contrast is considered to be the best focus position.
In auto exposure, a mean luminance level is conventionally measured for the entire image, over a region of interest, or over a multiple windows of the image. The mean luminance level is compared to a target level. The exposure is adjusted to minimize the difference between the mean luminance level and the target.
In auto exposure, it has been proposed to categorize the type of scene currently being exposed based on the luminance values of a set of predetermined image regions. Then, based on the determined scene categorization, the exposure can be adjusted more effectively.
Christmas tree is one of the scenes that frequently attracts picture takers. It is often featured with a dark background with many small lights. However, the current scene adaptive auto focus and auto exposure often fail for Christmas tree scenes.
Thus, there is need for devices, methods, and a computer readable medium for intelligently setting a camera's focus and exposure parameters for Christmas tree scene so that the images captured are of high quality. Here, the term “Christmas tree scene” is used not only for the night scenes with lighted Christmas trees, but also for the similar scenes that are composed mainly of a dark background with multiple small lights.